Pneumatic nailing machine



Oct. 22, 1968 A. cAsr ETAL 3,405,889

PNEUMATIC NAILING MACHINE Filed July 1, 196e 5 sheets-sheet 1 hel'r Afforney Oct. 22, 1968 A, CAST ETAL l 3,406,889

PNEUMATIC NAILING MACHINE Filed July 1, 196e 5 Sheets-sheet 2 Oct. 22, 1968 A. CAST ETAL 3,406,889

PNEUMATIC NA ILING MACHINE Filed July l. 1966 3 Sheets-Sheet 5 /nven lors:

Adolf CASTond Kur-f REICH ff heir AT'omey United States Patent O 3,406,889 PNEUMATIC NAILING MACHINE Adolf Cast, Oberlenningen, and Kurt Reich, Nurtingen, Germany, assignors to Karl M. Reich Maschinenfabrik, Wurttemberg, Germany, a German company Filed July 1, 1966, Ser. No. 562,249 Claims priority, application Germany, July 9, 1965,

R 4 ,0 12 Claims. (Cl. 227-130) ABSTRACT F THE DISCLOSURE The present invention relates to a pneumatic nailing machine which is provided with a hammering tool consisting of a striking pin or plunger on one end of a percussion piston which may be driven by compressed air within a cylinder which is connected via an air-inlet valve to a compressed-air supply line.

Prior to this invention, a pneumatic nailing machine of the above-mentioned type has been disclosed in the U.S. Patent No. 2,498,503, in which the cylinder containing the percussion piston is in addition connected to a reversing valve which at the end of each blow of the striking pin upon a nail is shifted by the percussion piston from its normal position to a reversing position in which by the action of this valve the piston is returned to its original inactive position, whereupon the reversing valve is automatically shifted back to its normal position in which another blow may be struck by the piston and striking pin upon the same nail. The machine is therefore designed so that the percussion piston and striking pin will strike repeated blows upon the nail until the latter is fully driven into a workpiece.

This known pneumatic nailing machine has, however, the disadvantage that the compressed-air inlet valve communicates with the main cylinder through thin channels and through the reversing valve, and that therefore the channels leading from the air-inlet valve to the main cylinder cause a considerable flow resistance so that when this valve is opened, it is not possible to produce immediately such a high pressure in the main cylinder that the percussion piston will be sufficiently accelerated for striking the required blows.

In order to overcome this disadvantage, other pneumatic nailing machines have been designed which are provided with a compressed-air inlet valve which is operated by compressed air and has a large inlet opening and is adapted to be controlled by a control valve via a control channel. These known nailing machines permit, however, only a single blow to be struck at each operation of an actuating member, forexample, a trigger. Therefore, if one blow is not suicient for driving a nail completely into a workpiece, the operator of the machine must operate the actuating member several times. However, even then he has no means of ascertaining whether the nail has been driven-in completely. It may therefore occur that the operator might move the machine to the next place where another nail has to be driven-in, even though the head of the previous nail still projects for a small distance from the workpiece and might then have 3,406,889 Patented Oct. 22, 1968 to be driven-in completely by hand. This is true especially when the operator of such a machine has to carry out a larger number of nailing operations as quickly as possible. Since he has then no time for checking whether a nail has been driven-in completely, he may have to effect an idle stroke of the percussion piston before drivingin the next nail since this nail cannot be fed to the machine until the piston has reached its lowest end position. Such idle strokes, in turn, are the cause of a premature wear of the machine, especially of its piston and buffer.

It is an object of the present invention to provide a pneumatic nailing machine of the type as first mentioned herein which is designed so as to hit repeated blows upon a nail during one operation 0f the actuating member and in which the compressed air is supplied as suddenly as possible to the main or working cylinder when the airinlet valve is opened which is for this purpose provided with the largest possible flow passage.

For attaining this object the present invention employs a pneumatic nailing machine of the type as lirst described herein, and it is a feature of the invention to provide this machine with a compressed-air inlet valve which has a large flow passage and is adapted to be operated by compressed air, with a control valve for controlling the operation of this air-inlet valve via a control channel, and further with a reversing valve which is interposed between two sections of the mentioned control channel.

By the provision and arrangement of these elements the advantage is attained in accordance with the invention that, when the control valve is opened, the reversing valve will adjust the air-inlet valve so as to cause the percussion piston to strike a succession of blows upon a nail. This is due to the fact that at the end orf each partial stroke of the percussion piston the reversing valve will be automatically adjusted from its normal position to its reversing position in which it closes the air-inlet valve and thereby causes the percussion piston to be returned to its original inactive position, and that when the piston reaches this inactive position, the reversing valve is again automatically adjusted to its normal position in which it causes the air inlet valve to open and thereby the percussion piston to strike another blow upon the same nail.

The operation of the reversing valve may be controlled in different manners without departing from the scope of the invention. Thus, for example, one preferred embodiment of the invention provides that a reservoir which may be of a conventional type and in which compressed air is accumulated during the power stroke of the percussion piston for the purpose of returning this piston to its original position after each blow be also connected by a channel to the reversing valve for reversing its operating position. The operation of reversing the position of this valve may therefore be effected in a very simple manner by means of the accumulated air pressure in the reservoir and as soon as the pressure in this reservoir has been built up to the required strength for returning the piston. This may be attained, for example, in such a manner that the rear part of the main cylinder chamber behind the piston which is connected with the compressed-air line during the power stroke of the piston is also connected by means of a throttling device, preferably in the form of a check valve, with the front part of the main cylinder chamber which is closed toward the outside during the power stroke of the pistons by the striker pin or plunger which is secured to the piston. The necessary pressure for returning the piston will thus be produced in the front part of the main cylinder chamber essentially at a time immediately after each impact of the piston and its striker pin upon a nail. Since for carrying out each impact the piston only requires a fraction of the time which is necessary until after stopping momentarily in its forward position it can be returned to its original position, the throttling device may be designed so that the compressed air passing therethrough during each power stroke of the piston will have practically no effect upon the power of the blow, and so that the pressure for returning the piston will only be built up to its required strength in the front part of the cylinder chamber at a time immediately after each impact. By connecting the front part of the cylinder chamber with the reversing valve and by designing this valve so that it will not reverse its position until the pressure in this front part has reached the required minimum strength for returning the piston, the result will always be definitely attained that the compressed-air inlet valve will not be closed until each impact has been completed. The front part of the cylinder chamber may for this purpose be connected to the air reservoir, while the throttling device may be provided in the form of a throttling opening either in the piston or between the piston and the cylinder wall or in the cylinder wall itself.

A modification of the invention for effecting the reversal of the reversing value consists in providing an aperture in the wall of the main cylinder which will be opened by the percussion piston during its power stroke so as to permit the compressed air driving the piston to pass therethrough, and in connecting this aperture with the reversing valve for reversing the operating position thereof. By this construction the result will be attained that the operation of reversing the position of the reversing valve will be dependent upon the distance of travel of the percussion piston during each power stroke. This feature may also be combined with one or both of the two other features as described above, for example, in such a manner that the aperture in the wall of the main cylinder serves as a throttle for producing the necessary pressure in the front part of the cylinder chamber or within the chamber serving as an air reservoir, and that these chambers are in communication with the reversing valve.

The prior art further discloses a pneumatic nailing machine which is provided with a compressed-air inlet valve the operation of which is also controlled by compressed air and the movable valve member of which is provided with two surfaces of different sizes which face in opposite directions and define two chambers. The chamber which is defined by the smaller surface communicates continuously with the compressed-air supply line, while the other chamber which is defined by the larger surface is adapted to be alternately connected by a control channel and the control valve either with the compressed-air supply line for closing the air-inlet valve or with the outer air for opening the inlet valve. The movable valve member of the control valve may be provided in the form of a piston, a cylindrical slide valve, or a diaphragm. According to the present invention, this known pneumatic nailing machine may be modified and further developed in such a manner that the control channel be connected with a chamber which contains the movable valve member of the reversing valve and is provided with two valve ports one of which is connected with a first channel leading to the control valve and the other with a second channel which is connected to a source of compressed air, that the valve member of the reversing valve serves for closing one or the other of these valve parts, and that resilient means, for example, a spring be provided for normally maintaining the valve member in the position in which it closes the valve port leading to the second channel. This second channel may be connected with the compressed-air reservoir and/ or with the aperture in the wall of the main cylinder. For shifting the valve member of the reversing valve from one position to the other, it is, however, also possible to provide a dierential piston, both sides of which may be acted upon by compressed air and the smaller side of which faces a chamber which communicates with the second channel leading to the compressedair supply line, while its larger side communicates with 4 the compressed-air reservoir and/or with the aperture in the wall of the main cylinder.

Another preferred feature of the invention consists in providing a valve at the front end of the main cylinder in a position so as t-o be acted upon by the percussion piston, it acts upon another piston which then returns the control valve to its inactive position. Consequently, when a nail after repeated blows thereon is completely driven into a workpiece, the control valve will be positively returned to its original inactive position and the operation of the machine will then be terminated. The valve which is thus actuated by the percussion pist-on may consist of an aperture in the main-cylinder wall which is opened by the percussion piston when it arrives in its most forward position so that the `compressed air in the rear part of the maincylinder chamber will then be supplied to the control valve so as to act upon the piston thereof. The valve may, however, also be one which is mounted at the front end of the main cylinder and is opened by the percussion piston and then supplied compressed air to the piston of the control valve.

The features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings, in which- FIGURE 1a shows a longitudinal section of a pneumatic nailing machine according to the invention in a position in which the air-inlet valve is closed and the percussion piston is in its upper inactive or rest position;

FIGURE 1b shows a longitudinal section of the left part of the nailing machine according to FIGURE l, but in a position in which the air-inlet valve is open and the percussion piston has arrived at the end of its power strokes; while FIGURE 2 shows a longitudinal section of a modification of a part of the machine according to FIGURE la.

As illustrated in FIGURE la, the pneumatic nailing machine according to the invention comprises a cylindrical housing 1 which is secured at one side to a grip 2 in which a chamber 3 is provided which is connected or adapted to be connected to a compressed-air supply line 10. Housing 1 contains a pair of concentric cylinders 4 and 5 which together with the housing 1 define two concentric annular chambers 6 and 7. The inner cylinder 5 forms a main or working cylinder which encloses a chamber 8 in which a percussion piston 9 with a striker pin or plunger 11 thereon is slidable. The lower ends of the annular chambers 6 and 7 and the chamber 8 of cylinder 5 are closed by a flange on a foot part 14 of the machine which is provided with a central bore 13 and a gasket ring 12 in the wall of this bore for sealing the Same completely when the striker pin 11 is inserted. During each power stroke of piston 9, the striker pin 11 passes into and through this bore 13 and the gasket 12 and then hits upon the head of a nail 16 which has previously been inserted into a nail channel 15 and is held therein by clamping jaws 17 which are disposed within radial slots in the foot 14 and are pressed radially against the nail 16 by a ring 18 of rubber or other resilient material. Nail 16 may be inserted into the nail channel 15 either through its open lower end or the machine may be provided with a nail feeding mechanism 16a of a conventional type which, after one nail has been ejected from the nail channel 15 and the piston with the striker pin 11 has been retracted, will feed another nail into the nail channel for the next nailing operation. Such nail feeding mechanisms are well known in the art and therefore do not need to be further described in detail. The lower end of the main cylinder 8 which is closed by the flange on the foot 14 contains a buffer 19 of rubber or a similar material for cushioning the impacts of piston 9 at the end of its last power stroke.

At their upper ends, housing 1 and main cylinder 5 are closed by a cap 21. For securing the housing, the cylinders 4 and 5, the foot 14, and cap 21 to each other, the upper and lower ends of cylinder 5 are provided with male threads which are screwed into female threads in the foot 14 and the cap 21 so that the end surfaces of housing 1 abut against the flange surfaces of the foot 14 and the cap 21. The upper end of the main cylinder chamber 8 contains a resilient mushroomlike locking member 23 which has a ange 22 on its upper end which is clamped between the upper end surface of cylinder 5 and the bottom of the cap 21. This resilient locking member 23 enters into a socketlike recess 24 in piston 9 when the piston is moved Aback to its upper end position in which it is then resiliently held by its engagement with the locking member 2.3.

The outer annular chamber 6 communicates directly with lchamber 3 in grip 2 `and will therefore always contain compressed air when the nailing machine is connected by thelair supply line to a source of compressed air. The upper lend of this outer annular chamber 6 is defined by an internal flange 25 on housing 1 which abuts against the upper end surface of the outer cylinder 4 which is provided Ywith radial apertures 26 directly underneath the internal-ange 25.

The chamber4 which is defined by the upper part of housing 1 and the upper part of the main cylinder 5 coutains a ycylindrical slide valve 27 which is slidable therein in the axial 'direction and has a lower rounded end 28 which, when this valve 27 is in its `closed position, en-` gages upon a' resilient gasket ring 29 which rests on an l internal flange 31 of the outer annular cylinder 4 and serves as avalve disk. This internal flange 31 `engages directly upon the outer surface 32 of a projection on the Iinainl cylinder 5 and thereby completely closes the upper endof the Iannular'chamber 7. The cylindrical outer surface'of slide valve 27 engages upon the cylindrical inner surface of the internal ange 25 which is additionally provided with a gasket ring 33. Y

'The annular chamber containing the cylindrical slide yvalve 27 is divided by theflatter into three annular chambers' 37, 38, and 39v which lare sealed relative to each other by gasket rings 33, 34, and 35. When slide valve 27 is in its open position, as shown in FIGURE lb, the annular chamber 37 communicates through the radial apertures 26'in the outer cylinder 4 vwith the outer-an'-k nu'l'ar chamber 6 whichis supplied withcompress'ed air, and when'the valve member 27 is closed, as shown in FIGURE' la, it also closes the annular chamber 37 relativev to the outer annular chamber 6. The annular chamber 37 further communicates through apertures 41 with the partialchamber 42, of the main cylinder chamber 8 which is located behindT piston'9. Slide valve 27 is further pro# vided with radial channels 43 which connect the annular chamber 37 with the annular chamber 38 when slide valve 27 is in its closed'position. Chamber 38 communicates through radial channels` 44 in 'housing 1 with the outer air. :The nannular chamber 39 which is associatedwith the largest' end surface 45 of slide valvev 27 communicates through a control channel 46 with a chamber 47 in the grip '2 in which the valve member 48 ofa reversing valve is located which is generally'indi'cated by the numeral 49. This valve member 48 is adapted to close either one `or'the other of two opposite valve ports 51 and 52. Valve port 51 communicates through a channel 53 with a c'ontrol valve'v 54, which valve port 52 leads to a cylinder chamber S5 in'which a differential piston 56 is slidable which is positively lconnected to the valve member 48 by means of a valve rod 57. The part 58 of chambernSS which contains the valve rod 57 andis provided with the valve port 52 communicates through a channel 59 with the outer annular chamber 6 which always contains compressed air. The other part 6 1V of chamber 55 which faces the larger-end surface of the differential piston 55'communicates through a channel 62 with inner annular chamber 7 which, in` turn, is connected with the main cylinder `chamber 8 by radial apertures 63 Vin the central part of cylinder 5 and by radial apertures 64 in the lower end of cylinder 5. The upper apertures 63 are normally closed on theA outside by aV resilient rin/g 65 which surrounds vthe cylinder 5 and forms a check valve. Due to the pressure of the compressed air in the part 58 of chamber 55, valve member 48 of the reversing valve 49 is normally maintained in the position as illustrated in FIGURE 1a, in which the valve port 52 is closed and the control channel 46 communicates with the channel 53 which leads to the control Valve 54.

This control valve 54 is provided with a chamber 67 which is connected to the channel 53 and contains a valve member 66 which is adapted to close one or the otherof two opposite valve ports 68 and 69. Valve port 68 leads to the chamber 3 in the grip 2 which is always under air pressure, while valve port 69 leads through a channel 70 to the outer air. The body of grip 2 further contains a bore 71 in which a valve tappet 72 is slidable which passes through the valve port 69 and carries a piston 74 which is slidable within a cylinder chamber 73. The lower end of valve tappet 72 projects downwardly from this chamber 73 and engages at the outside of grip 2 upon a trigger 76 which is pivotable about an aXis 75. The part of cylinder chamber 73 facing the valve member 66 communicates through a channel 77 with a valve 78 which is provided at the lower end of the main cylinder chamber 8. Valve member 79 of this valve 78 is normally pressed by a spring 81 upon its valve seat and thereby interrupts the connection between the end of channel 82 in the valve housing 83 with the outer annular chamber 6 whichcontains compressed air. The bottom of valve housing 83 is provided with a bore in which a valve tappet 85 is slidable. The end of this bore facing the main cylinder chamber 8 contains a ball 86 which projects into this chamber 8. Thus, after the trigger 76 has been pulled and the control valve 54 has thereby been opened and the striker pin 11 on piston 9 has repeatedly hit upon a nail 16 until the piston reaches its most forward position at the end of its last power stroke, as illustrated in FIGURE 1b, the piston depresses the ball 86 which, in turn -presses against the valve tappet 85 and thereby lifts the valve member 79 of its seat so that compressed air will then ow from the outer annular chamber 6 through channel 77 into the chamber 73'and move the control valve 54 back to its inactive position, as shown in FIGURE la, in which compressed air passes from chamber 3 to grip 2 through the valve port 68 and channel 53, the reversing valve 49, and channel 46 to the annular chamber 39 and thereby moves the cylindrical slide valve 27 to its closed position.

The mode of operation of the machine is as follows:

When trigger 76 is pulled at a time when the percussion piston 9 is held in its retracted position as illustrated in FIGURE la, valve tappet 72 will be pushed upwardly so that the valve member 66 will close the valve port 68. Valve chamber 67, channel 53, chamber 47 of the reversing valve 49, channel 46, and the annular chamber 39 will thereby be vented through channel 70. The compressed air passing through the apertures 26 will then -act upon the front end 28 of slide valve 27 and shift the same upwardly to the position as shown in FIGURE 1b, so that compressed air will then penetrate suddenly through the apertures 26, the annular chamber 37, and the apertures 41 into the upper part 42 of the main cylinder chamber 8 and propel the percussion piston 23 forwardly so that the striker pin 11 will hit upon a nail 16.

In order to hold the trigger 76 more easily in its pulled position against the action of the compressed air in the valve port 68 pressing the valve member 66 against the valve tappet 69, the latter is provided with a groove 89 into which a ball 87 will then engage which is acted upon by a spring 88.

Before the trigger 76 is pulled and during the power stroke of the percussion piston 9, the reversing valve 49 will be maintained in its normal position as illustrated in FIGURE la by the pressure prevailing in the part 58 of chamber 55. When trigger 76 is then pulled to operate the control valve 54, the annular chamber 39 will be connected through the control valve 54 and the channel 70 wit-h the outer air so that the cylindrical slide valve 27 will then be held in the open position as illustrated in FIGURE 1b. As soon as the percussion piston 9 has passed the radial apertures `63, compressed air will ow through these apertures into the inner annular chamber 7 which forms an air reservoir. When the pressure in the annular chamber 7 has reached a certain strength at the end of a stroke, the differential piston 56 of the reversing valve 49 will be moved upwardly so that its valve member 48 will close the valve port51 and open the valve port 52. Compressed air will then pass rfrom the outer annular chamber 6 through the reversing valve 49 and the channel 46 into the annular chamber 39 and close` the slide valve 27, whereby at the same time the part 42 of the main cylinder chamber 8 is vented through the radial channels 43 and 44. The compressed air which was stored in the annular chamber 7 then passes from the latter through the apertures 64 into the lower or front part of the main cylinder chamber 8 and propels the percussion piston 9v back to its neutral position. As soon as the striker pin 11 emerges from the bore 13, the part of chamber 8 which is then in front of the piston 9 and thus also the annular chamber 7 will be vented through the apertures 64, the bore 13, and the nail channel 15. This has the result that the differential piston 56 will be moved back by the compressed air in the part 58 of cylinder 55 and that the reversing valve 49 will thereby be moved back to its normal position, as illustrated in FIGURE la, in which as long as the trigger is pulled and the control valve 54 is thereby actuated, the annular chamber 39 will be vented so that the percussion piston will then carry out another stroke in the same manner as previously described.

This cycle of operations will be repeated until the percussion piston 9 actuates the valve 78 so that the compressed air which then passes into the cylinder chamber 73 will return the control valve 54 to its original inactive position.

Since the compressed air which is then in the cylinder chamber 73 cannot emerge therefrom if the piston 74 is in t-ight sealing engagement with the wall of this chamber, this chamber should be connected with the outside air by an adjustable throttling device so that, after the control valve 54 has been returned to its inactive position, the compressed air will escape from chamber 73 within an adjustable period of time. In FIGURE la, this adjustable throttling device has been indicated in dotted lines merely in the form of a choke bore 73' of a suitable diameter Which may be determined by tests. Of course, this choke bore may also be of a larger diameter, and a setscrew may be provided for adjusting its effective diameter.

FIGURE 2 illustrates a simpliiied modification of the reversing valve 149. The valve member 148 of this valve is held in its normal position by the action of a spring 156. The valve port 152 which is then closed by the valve member 148 is connected by a channel 162 with the inner annular chamber 7, as shown in FIGURES 1a and lb. Consequently, the compressed air which is stored within the inner annular chamber 7 not only effects the reversal of valve 149 as described with reference to the reversing valve 49 according to FIGURE la, but it also serves at the same time flor closing the tubular valve -member 27. In all other respects, the mode of operation of the apparatus as illustrated in FIGURE 2 is the same as previously described with reference to the apparatus according to FIGURES l'a and lb.

While in the embodiments ofthe invention as previously described the control valve 54 is provided with a piston 74 for returning the valve to its neutral position, it is also possible to dispense with this piston 74, in which case the control valve 54 will be returned to its neutral position by the compressed -air pressing upon the valve member 66 and the valve tappet 72 when the trigger 76 is released.

Valve 78 which is actuated by the percussion piston 9 when it reaches the lower end of chamber `3 may also be connected by a conduit 77 with a nail feeding mechanism, not shown, so as to feed a new nail into the nail channel 15 when valve 78 is opened.

Although our invention has been illustrated and described vvith reference to the preferred embodiments thereof, we wish to have it understood that it is in no way limited to the details of such embodiments but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed our invention, what we claim is:

1. A pneumatic nailing machine comprising a main cylinder, a nail channel on one end of said cylinder adapted to receive a nail, a percussion piston having a striker pin thereon and adapted to reciprocate longitudinally Within said cylinder from an inactive position at the rear end of said cylinder for striking repeated blows by means of said striker pin upon said nail in said nail channel until said nail is driven completely into a workpiece, said cylinder having a pressure chamber behind said piston, said pressure chamber having a large inlet opening, an inlet valve movable between a closing position and an opening position for closing and opening said inlet opening, respectively, and having a large owpassage when in its open position, pneumatically actuated means for moving said inlet valve, iirst conduit means for supplying compressed air through said inlet opening to said pressure chamber when said inlet valve is in said open position for driving said piston forwardly from said rear end position, iirst means for venting said pressure chamber when said inlet valve is in its closed position, means for moving said piston from the position in which it is located at the end of each blow to said rear end position, a manually actuated control valve having a iirst inactive and a second active position, second venting means, a conduit connecting said pneumatically actuated means by said control valve in its iirst position with said first conduit means for holding said inlet valve in its closing position by the pressure of the compressed air and in its second position with said second venting means for opening said inlet valve, a reversing valve interposed in said conduit between said control valve and said pneumatically actuated means and thereby dividing said conduit into a first part between said control and reversing valves and a second part between said reversing valve and said pneumatically actuated means, an air chamber adapted to contain compressed air, said reversing valve having a rirst normal position and a second reversing position, said reversing valve in its tirst position connecting said two conduit parts directly with each other for maintaining said inlet valve in said closing position when said control valve is in its first position and for opening said inlet valve when said control valve is in its second position, means for moving and normally maintaining said reversing valve into and in its Aiirst position respectively when said piston is in its rear end position, second conduit means for supplying compressed air to said reversing valve for moving it from its first position to its second position when said piston has substantially completed each blow upon said nail, thereby moving said inlet valve to its closing position by means of the compressed air contained in said air chamber and for simultaneously venting said pressure chamber to permit said piston to move to its rear end position.

2. A pneumatic nailing machine as defined in claim 1, in which said air chamber is connected with said compressed-air supply means.

3. A pneumatic nailing machine as deiined in claim 1, further comprising a reservoir connected with a front part of said cylinder for accumulating the air compressed by each power stroke of said piston in said front part when said striker pin has entered said nail channel and has thereby closed said front part of said cylinder toward the outer air.

4. A pneumatic nailing machine as defined in claim 3, in which said means for moving said reversing valve comprise an actuating cylinder, a differential piston slidable within said actuating cylinder and connected to said reversing valve and having a larger side and a a smaller side, said differential piston dividing said actuating cylinder into two parts, one of said cylinder parts facing said larger piston side being connected with said reservoir and the other cylinder part facing said smaller piston side being connected with said compressed-air supply means so that after each blow of said piston upon said nail the pistoncompressed air from said front part of said main cylinder and said reservoir acts upon said larger piston side to move said reversing valve from its first normal position to its second reversing position so that compressed air then passes from said compressed-air supply means through said first cylinder part and said second conduit part to said pneumatically actuated means so as to move said inlet valve to its closing position and at the same time to vent said pressure chamber through said first venting means so that after each -blow said piston will then be returned by said piston-compressed air to its rear end position, said differential piston being adapted to move said reversing valve back to its normal first position as soon as said striker pin during the return movement of said piston has been withdrawn from said nail channel so that said front part of said main cylinder is vented through said nail channel.

5. A pneumatic nailing machine as defined in claim 1, further comprising throttling-channel means connecting said pressure chamber with said front part of said main cylinder when said striker pin during each power stroke of said piston enters said nail channel and thereby closes the front end of said cylinder toward the outer air so as to increase the pressure of the piston-compressed air in said front part of said cylinder for returning said piston to its rear end position after each blow of said striker pin upon said nail, and channel means connecting said front part of said cylinder with said reversing valve for moving the same from said first normal to said second second reversing position.

6. A pneumatic nailing machine as defined in claim 5, in which said throttling-channel means comprise at least one check valve.

7. A penumatic nailing machine as defined in claim 3, in which said reservoir comprises an annular chamber around said main cylinder, and further comprising at least one check valve inthe wall of said cylinder for connecting said pressure chamber with said reservoir when said front part of said cylinder is closed by said striker pin for increasing the pressure of the piston-compressed air in said front part for returning said piston to its rear end position after each blow of said striker pin upon said nail, and channel means for passing said piston-compressed air from said front part and said reservoir to said reversing valve for moving the same from its first normal to its second reversing position.

8. A pneumatic nailing machine as defined in claim 5, in which said throttling-channel means are provided in the wall of said main cylinder so that compressed air is passed from said pressure chamber through said throttling channel means and then to said reversing valve when said piston has passed said throttling-channel means during each of its poser strokes.

9. A pneumatic nailing machine as defined in claim 1, further comprising an actuating member for moving said control valve from its first to its second position, said inlet valve forming a valve chamber, a cylindrical pistonlike slide member movable within said chamber and having two surfaces of different sizes facing in opposite directions and each adapted to be acted upon by compressed air and separating said valve chamber into two parts, one of said chamber parts defined by the smaller surface of said valve member being continuously connected with said compressed-air supply means, and the other chamber part defined by the larger surface of said valve member being connected by said conduit and said reversing valve in its first position and said control valve and said second venting means alternately to the outer air when said control valve is moved -by sa'id actuating member from its first inactive to its second active position or to said compressedair supply means when said actuating member is released.

10. A pneumatic nailing machine as defined in claim 1, in which said means for normally maintaining said reversing valve in its first position consists of a spring.

11. A pneumatic nailing machine as defined in claim 1, further comprising an actuating member for moving said control valve from its first to its second position, a further cylinder, a piston slidable within said further cylinder, a valve tappet secured to said piston and adapted to engage at one end upon said actuating member and at the other end upon said control valve, a further valve at the front end of said main cylinder and connected to said compressed-air supply means and adapted to be opened by said percussion piston when it reaches the front end of said main cylinder, and conduit means connecting said further valve to said further cylinder for supplying compressed air from said supply means to said further cylinder for returning said valve tappet and said piston thereon and said actuating member to their original positions.

12. In a pneumatic nailing machine as defined in claim 11 a'nd being adapted to be operatively associated with an automatic nail feeding mechanism, a conduit for connecting said further valve to said nail feeding mechanism for supplying compressed air thereto for operating the same when said nail has been completely driven by said percussion piston and striker pin from said nail channel into a workpiece.

References Cited UNITED STATES PATENTS 2,887,686 5/ 1959 Wandel et al. 227-130 2,997,713 8/ 1961 Anstett 227-130 XR 3,023,413 3/ 1962 Fischer et al 227-130 XR TRAVIS S. MCGEHEE, Primary Examiner. 

